In Japanese Patent Application Publication No. 2003-243392, a conductive cobalt-tungsten-phosphorous (CoWP) film which is selectively grown by an electroless plating method using as a catalyst a copper wiring line copper wiring line is used as a cap film of the copper wiring line copper wiring line.
However, the CoWP film formed by an electroless plating method using as a catalyst the copper wiring line is isotropically grown on the wiring line. Therefore, as the thickness of the CoWP film is increased, the CoWP is formed on an interlayer insulating film as well as on the copper wiring line. When copper is not completely removed and a residue of copper remains on the interlayer insulating film, the CoWP film is also formed on the residue.
In other words, the CoWP film has an insufficient selective growth property.